Technical Abstract:
Utilization of renewable resources, particularly when these substrates are waste proteins, makes economic sense in an environment where petroleum feedstuffs are becoming too expensive for a good cost-effective return. In this regard, we have proposed the utilization of enzymatically modified waste proteins from the leather (gelatin) and dairy (casein and whey) industries as fillers in leather production. In the initial experiments, proteins were prepared with fluorescent labels and blends of these labeled proteins were then applied to microbial transglutaminase-pretreated blue stock. Biopolymers, prepared by enzymatically modifying varying combinations of the labeled proteins, were characterized with respect to physical properties and molecular weight distribution, and products that showed potential (low viscosity and melting point) were also applied to enzyme-treated blue stock. Using epi-fluorescent microscopy, we determined that the fillers, from both treatments, were evenly distributed in the leather and not removed by washing. We then treated various areas in the hide (butt, belly, and neck) with the products, retanned, colored and fatliquored the treated pieces, evaluated them with respect to subjective properties against controls and finally determined mechanical properties. The results from these tests show that the mechanical properties were not significantly affected by the treatment and subjective properties, e.g., handle, fullness, break and color, were improved over the controls. Fillers thus have the potential to be economically produced from sustainable resources as an alternative to more expensive and increasingly limited conventional products.